AI Article Synopsis
- The testosterone-estradiol binding protein (SBP) was isolated from human placental blood and labeled using a specific radiation technique to study its structure.
- Analysis through high-performance reverse-phase liquid chromatography revealed two main peaks of radioactivity linked to distinct peptide sequences associated with the protein.
- The sequence comparison suggested that the radioactive labeling primarily occurred at the Met-139 residue within a hexapeptide fragment, providing insights into the protein's structure and function.
Article Abstract
The testosterone-estradiol binding protein (sex binding protein = SBP), immunopurified from human placental blood, was photolabelled by irradiation at lambda greater than 300 mm in the presence of tritiated 17 beta-hydroxy-androsta-4,6-dien-3-one. High-performance reverse-phase liquid chromatography of tryptic peptides, showed two main peaks of radioactivity. Sequence determination of these two fractions indicated that the radioactivity was associated with an undetectable amino-acid preceded either by the sequence His-Pro-Ile (major peak) or Arg-His-Pro-Ile at the N-terminal site and bearing Arg as C-terminal amino-acid. Comparison with the sequence reported for human SBP (K.A. Walsh et al., Biochemistry, 25, 1986, pp. 7584-7590) suggested that radioactive labelling was localized on the Met-139 residue of the hexapeptide Arg-His-Pro-Ile-Met-Arg (fragment 135-140).
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